1. Field of the Invention
This invention relates to an information signal recording apparatus having a function of correcting a time base error included in the information signal.
2. Description of the Related Art
The output of a magnetic head of, for example, a magnetic recording and reproducing apparatus includes a time base error due to the uneven rotation of the magnetic head, fluctuations in the traveling speed of tape or the like. If a reproduced video signal is supplied to a monitor without correction, the error results in transverse swaying of images on the picture plane or fluctuations of chromaticity. To avoid this, a time base error correction circuit is provided for correcting the time base of the video signal. Meanwhile, with respect to a video display, time base error correction is not absolutely necessary for a luminance signal. However, time base error correction is indispensable to a chrominance signal as a time base error causes uneven colors, etc. It has been practiced, therefore, to carry out time base error correction at the time of performing a frequency converting process for bringing into its original state the chrominance signal which is low-band converted for recording.
With a video signal reproduced by the magnetic recording and reproducing apparatus arranged in the above stated manner, the luminance signal component of the video signal includes some time base error while the chrominance signal component thereof may not include any time base error. Therefore, in carrying out dubbing, for example, the time base error included in the luminance signal component of the original video signal causes the luminance signal component of the duplicate record to include the time base error. Then, in reproducing the duplicate record obtained by dubbing, the time base error recurs in a cumulatively enhanced manner. This results in a great degradation of the reproduced picture. Such time-base error accumulation eventually makes the time base error incorrigible at the time of frequency converting the low-band converted chrominance signal back to its original state.
The known time base correction circuits for correcting the above stated time base error include a so-called time base corrector. The time base corrector is arranged in principle to correct the time base error by varying, according to the degree of the error, the delay time of a variable delay line. However, the variable delay line brings about some deterioration in the frequency characteristic and the S/N ratio of the video signal. While the degree of the signal deterioration is not much and presents no problem in obtaining the reproduced video signal from a magnetic tape, it is greatly detrimental to a broadcasting signal which is very stable including no time base error.